Java中=+运算符的使用？

Use of =+ operator in Java?

提问by Gokul Nath KP

I've the following code:

我有以下代码：

public class Operators {
    public static void main(String[] args) {
        int i =+ 2;
        System.out.println(i);
    }
}

Upon executing I'm getting the following output: 2

执行后，我得到以下输出：2

So what does =+operator actually does here?

那么=+运算符在这里实际上是做什么的呢？

EDIT:

编辑：

As some answered, it is assigning +2to i, consider the following code:

正如一些人回答的那样，它正在分配+2给i，请考虑以下代码：

public class Operators {
    public static void main(String[] args) {
        int i =- -2;
        System.out.println(i);
    }
}

So in above case, output should be -2. But I'm getting 2

所以在上面的情况下，输出应该是-2. 但我得到2

So I suppose, it is -(-2), which gives 2. Right?

所以我想，它是-(-2)，它给出了2。对吗？

采纳答案by Subhrajyoti Majumder

int i =+ 2;

It is positive 2(+2) assignment to variable i. It is more miningful or understandable if your write like -- int i = +2;

对变量 i 进行正 2(+2) 赋值。如果你写的像——int i = +2;

One more example -

再举一个例子——

int i = 2;
i=+3;
System.out.println(i);

It prints 3.

它打印 3。

+Unary plus operator; indicates positive value (numbers are positive without this, however)

+一元加运算符；表示正值（然而，没有这个数字就是正值）

More example - http://docs.oracle.com/javase/tutorial/displayCode.html?code=http://docs.oracle.com/javase/tutorial/java/nutsandbolts/examples/UnaryDemo.java

更多示例 - http://docs.oracle.com/javase/tutorial/displayCode.html?code=http://docs.oracle.com/javase/tutorial/java/nutsandbolts/examples/UnaryDemo.java

回答by Red Alert

You are setting i equal to +2, which is what you got. What kind of output are you expecting?

您将 i 设置为 +2，这就是您得到的。你期待什么样的输出？

回答by devnull

Upon saying:

在说：

int i =+ 2;

+acts as a unary operator.

+充当一元运算符。

To elaborate, it sets ito a positive value 2.

详细地说，它设置i为正值2。

EDIT: Your update says:

编辑：您的更新说：

int i =- -2;

produces 2. Why?

产生 2. 为什么？

In this case, it implies that i=-(-(2)). Note that using a unary minus operator might produce unexpectedresults when the value is, say, Integer.MIN_VALUE.

在这种情况下，它意味着i=-(-(2))。请注意，当值为 时，使用一元减运算符可能会产生意外结果，例如Integer.MIN_VALUE。

回答by user2841290

I believe what you mean by =+ is really +=.

我相信您所说的 =+ 确实是 +=。

Your code is assigning the value of +2 (positive 2) to the integer.

您的代码正在为整数分配 +2（正 2）的值。

For example:

例如：

int x =+ 4;
x =+ 8;
Console.WriteLine(x.ToString());
Console.ReadLine();

Will print "8", not 12. This is because you are assigning x to +4 and then +8.

将打印“8”，而不是 12。这是因为您将 x 分配给 +4 然后 +8。

If you are asking about what += does, it is a shorthand to takes the initial variable and add to it.

如果您要问 += 的作用，那么获取初始变量并将其添加到其中是一种简写。

x += 8

is the same as

是相同的

x = x + 8

By changing the previous example form =+ to += give us:

通过将前面的示例形式 =+ 更改为 += 给我们：

int x = 4;
x += 8;
Console.WriteLine(x.ToString());
Console.ReadLine();

Will print "12".

将打印“12”。

回答by Aniket Thakur

Refer to the following image for unary operators.

有关一元运算符，请参阅下图。

Here is an exmaple to understand it.

这是一个理解它的例子。

public class UnaryDemo {
    public static void main(String[] args) {
        int x = 10;
        int y = 20;

        int result = +x;

        System.out.println("+x = " + result);

        result = -y;

        System.out.println("-y = " + result);
        }
    }

and the output is

输出是

+x = 10
-y = -20

So think the operator as variable = +valuerather than variable =+ values. yeah That space makes it more readable.

因此，将运算符视为variable = +value而不是variable =+ values。是的，这个空间使它更具可读性。

回答by Aniket Kulkarni

As all others are answered, I want to give the JLS reference.
Answer to your Edit

正如所有其他人的回答一样，我想提供 JLS 参考。
回答您的编辑

int i =- -2;

As specified in jls

按照jls 中的规定

• Unary numeric promotion (§5.6.1) is performed on the operand.
• The type of the unary minus expression is the promoted type of the operand.
• At run time, the value of the unary minus expression is the arithmetic negation of the promoted value of the operand.

• 对操作数执行一元数值提升（第 5.6.1 节）。
• 一元减号表达式的类型是操作数的提升类型。
• 在运行时，一元减表达式的值是操作数提升值的算术否定。

So,

所以，

System.out.println(i); //prints 2  

For integer values, negation is the same as subtraction from zero.

对于整数值，否定与从零中减去相同。

---

---

Note

笔记

For floating-point values, negation is not the same as subtraction from zero, because if x is +0.0, then 0.0-x is +0.0, but -x is -0.0.

对于浮点值，否定与从零减法不同，因为如果 x 为 +0.0，则 0.0-x 为 +0.0，而 -x 为 -0.0。

Unary minus merely inverts the sign of a floating-point number. Special cases of interest:

一元减号只是反转浮点数的符号。感兴趣的特殊情况：

• If the operand is NaN, the result is NaN. (Recall that NaN has no sign (§4.2.3).)

• If the operand is an infinity, the result is the infinity of opposite sign.

• If the operand is a zero, the result is the zero of opposite sign.

• 如果操作数为 NaN，则结果为 NaN。（回想一下 NaN 没有符号（第 4.2.3 节）。）

• 如果操作数是无穷大，则结果是相反符号的无穷大。

• 如果操作数为零，则结果为相反符号的零。

Useful links

有用的链接

1. unary operators
2. Unary Numeric Promotion

1. 一元运算符
2. 一元数字提升